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experiment, you’re going to use what we’re going to focus on with
chemicals. How much of each one this unit. One way chemists figure
you use is going to change the this out is by writing a balanced
results you get, so it’s important to chemical equation to describe a
find a way to accurately measure chemical reaction (more on this
out the same amount of chemical later). Once you learn how to
each time. Always use a container balance the atoms and charges in a
to hold your chemicals – never chemical reaction, you can figure
place them directly on the scale out the energy of the reaction as
itself. well.
Most chemist use an accurate Physical and Chemical Changes
balance to weigh out solids and A chemical reaction happens when
liquids. For example, if you need a chemical change (something that
0.1 mole of HCl (l), you could produces a new substance, like
calculate the volume of burning wood into ash, rusting a
concentrated HCl that contains 0.1 nail, decomposing a dead tree… all
mole of acid and then use a these take the starting materials
graduated cylinder (37% 12M). (reactants) and creates new
substances (products). On the flip
Here’s another way to do it: you
side, a physical change happens
already know that the gram-
when a sheet of paper gets wadded
molecular mass is 36.5
up, a banana is cut in half, etc.
grams/mole (from the periodic
table), so you can quickly figure Chemical reactions usually mean
out that you need 3.65 grams for the movement of electrons or
0.1 mole by doing this calculation: protons, leading to linking up or
breaking chemical bonds. There
(3.65 grams) / (0.37grams/gram
are many different kinds of
of solution) = 9.85 grams of the
chemical reactions:
acid solution. So place a container
on the scale, hit tare, and fill it Combustion: A combustion
with your solution until the scale reaction gives off energy, usually in
reads 9.85 grams. the form of heat and light. The
reaction itself includes oxygen
combining with another compound
Chemical Reactions to form water, carbon dioxide, and
other products. A campfire is an
Learning how to figure out whether
example of wood and oxygen
a chemical reaction will occur and
combining to create ash, smoke,
what comes out the other end is
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