Today we are going to make an explosive lunch!
You will need
- One small (sandwich size) zip-lock plastic bag
- Bicarbonate of soda
- Warm water
- A tissue
Do this experiment outside, or at least in the kitchen sink. Put about a quarter of a cup of warm water in the bag with half a cup of vinegar.
Put three teaspoons of the bicarbonate of soda into the middle of the tissue and fold it up into a little parcel.
Partially zip the bag closed but leave a little space to add the bicarbonate of soda parcel in. Put the tissue parcel in the bag and quickly zip the bag completely closed.
Put the bag on the ground and step back. The bag will start to expand and hopefully pop!
The bicarbonate of soda and the vinegar eventually mix together, the tissue just gives you enough time to get the bag shut. A reaction takes place between the alkaline bicarbonate of soda and the acidic vinegar, this is know as an acid-base reaction. The reaction produces carbon dioxide, which begins to fill the bag. After a while the bag can no longer hold any more gas so it pops!
The reactions between acids and alkalis are used lots in real life too. Farmers can treat acidic soil with alkaline lime fertilisers to neutralise the soil and allow plants to grow. It’s also a good way to treat a wasp sting; wasp stings are alkaline so you can treat them by putting vinegar on the sting.
New coins are always bright and shiny but they quickly become dull and tarnished. Today we are going to make our coins shiny again!
You will need 100ml of vinegar, some tarnished copper coins and a bowl.
Pour the vinegar into the bowl and add the salt. Mix until the salt is dissolved.
Try dipping a coin in and holding it there for 5 minutes. See how half becomes really shiny!
Put all your coins in and leave for 30 minutes. If you put lots of coins in the vinegar may turn green.
Make sure you rinse all the coins with clean water.
Coins become dirty due to oxygen in the air reacting with the metal to form copper oxide. They become darker as they age as the oxide layer increases. Vinegar is an acid (acetic acid) which can be used to clean up surfaces and remove the unwanted oxides. Acids release positively charged hydrogen atoms, also known as Hydrogen ions (H+) which react with the negatively charged oxygen in copper oxide and produce water (H2O). The copper that was linked to the oxygen dissolves leaving a nice shiny surface.
If your vinegar turned green this is due to all the copper dissolving and producing copper acetate.
Real World Applications
Iron that is used to make cars, trucks and boats can also react with the oxygen in the air and oxidise, producing rust. If a car gets rusty, mechanics can use phosphoric acid to remove it. It reacts with the rust, removing the oxide and replacing it with a layer of iron phosphate. This also protects the metal from rusting further.
Phosphoric acid is also found in coca cola, which is why it is so good at dissolving your teeth!
We’re feeling very festive this Tuesday so we thought it was the perfect time to make snow with science. All you need for this one is some shaving foam and bicarbonate of soda.
Simply mix the bicarbonate of soda and shaving foam together in a bowl until you get a powdery consistency.
Pick it up and have a play – you might notice that your fake snow actually feels cold too. This is due to the reaction between the bicarbonate of soda and the shaving foam. The reaction is endothermic meaning that it requires heat to occur, it takes this from the environment and so decreases the temperature around it.
The Science of Shaving Foam
Do you think shaving foam is a liquid or a solid? It’s actually a colloid. A colloid is a substance which has droplets of one state surrounded by another state. There are lots of different types of colloids with different combinations of states making up the droplets and the surrounding. In the case of shaving foam, the droplets are gas and the surrounding is liquid making it a foam colloid.
Happy Halloween! We all like being scared sometimes, whether it’s scary movies or a rollercoaster, but why do we get scared?
We feel fear when we see or hear something that makes us anticipate harm. If you are walking through a haunted house this Halloween and a skeleton jumps out at you, the skeleton is a stimulus that triggers a signal in your brain.
The hypothalamus is part of your brain that activates the ‘fight or flight’ response. When you are scared molecules of glutamate (a neurotransmitter) travel to the hypothalamus. This then triggers the autonomic nervous system, a response that you can’t control.
Nerves from the brain carry impulses to glands which produce adrenaline, released into the blood. Adrenaline causes our heart rate and blood pressure to increase making us ready to run away quickly.
When we get scared we also get goosebumps. This is a trait that evolved in our hairier ancestors. When our hair stands up on end it makes us look bigger and more threatening to whoever is scaring us. This is seen in other animals too, such as cats.
However, we aren’t scared forever. Eventually our body realises that there is nothing to be worried about. Sensory data of what we have seen and heard is sent to the hippocampus in the brain which can store and retrieve conscious memories. It gives context to what we have seen and asks questions such as have I seen this before and what happened last time?
If a skeleton jumps out, we will realise that it isn’t real and is probably just someone dressed up! The hippocampus will determine that there is no danger and sends a message to the hypothalamus. Adrenaline production stops and our heart rate goes back to normal.
We have evolved to feel fear to allow us to survive. People and animals who feared the right things survived and passed on their genes. This makes sure we don’t do stupid things like picking up poisonous snakes or walking off buildings.