ModuleNotFoundError when using python venv even though pip freeze shows the packages are installed

I am new to venv and virtual environments for Python in general. I created an environment called .venv using:

python3 -m venv .venv

I then activated it and installed some packages. When I list the packages using pip freeze, I get the following:

(.venv) $ pip freeze
boto==2.48.0
bz2file==0.98
certifi==2017.7.27.1
chardet==3.0.4
click==6.7
...

However, if I try to import any of these packages, I get a ModuleNotFoundError, e.g.:

(.venv) $ python -c 
"import click"
Traceback (most recent call last):
  File "<string>", line 1, in <module>
ModuleNotFoundError: No module named 'click'

What am I missing???